Mikhail Mikheenkov

Understanding the reaction kinetics of iron oxide reduction by carbon is a key task of the theory of metallurgical processes. One of the understudied features of the reaction kinetics of iron oxide solid-phase reduction by carbon is the discrepancy between the reacting substances’ small contact area and the process’s high rate. A convincing theoretical and experimental explanation of this effect has not yet been obtained. The data obtained earlier show that an increase in the scale of the briquetting pressure from 0 to 300 MPa increases the degree of its metallization during heating two-fold, and the metallization temperature decreases by more than 40 °C. Therefore, it was assumed that these effects during heating are a consequence of the mechanochemical activation (MCA) of iron oxides in the scale during its pressing. This paper presents the results of experimental studies on the influence of two types of scale MCA (grinding and pressing) on iron oxide reduction. The study of the MCA effect on the reaction kinetics of scale iron oxide reduction by carbon is a promising way to assess the criteria for scale phase composition changes under external factors. The presented results indicate a decrease in the amount of trivalent iron oxide (Fe₂O₃) after the MCA and an increase in the amount of one-and-a-half oxide (Fe₃O₄) and bivalent iron oxide (FeO). The obtained experimental data show that the initial stage of iron oxide reduction, consisting in the transition from higher iron oxides to lower ones, is possible at room temperature without carbon presence.

The processes of iron oxides’ reduction have a complex physicochemical mechanism, with the participation of solid, liquid, and gaseous substances. The article discusses the existing models for the reduction of iron oxides and provides data on the thermodynamic possibility of carrying out the reactions of their reduction through the solid and gas phases. Experimental data on the reduction of iron from industrial scale, obtained by the DSC (differential scanning calorimetry) method, show the kinetic dependence of the rate and completeness of recovery on external factors: pressing pressure during sample preparation and the reagents’ composition. The pressing pressure, under conditions of iron ions’ solid-phase diffusion, has the significant effect by increasing the reagents’ contact area. Under conditions of iron ions’ comprehensive diffusion, the pressing pressure does not affect the reduction processes rate. The introduction of 10 mass.% flux into the raw mixture composition leads to a partially liquid-phase diffusion of iron ions and weakens the effect of the pressing pressure in this process. An ion diffusion-catalytic mechanism is proposed to describe the observed effects during the reduction of iron oxide of technogenic origin.

The overview of existing models for iron oxides reducing and an analysis of their applicability to technogenic formations is presented. The thermodynamic analysis data of iron oxides reducing reactions through solid and gas phases and experiment results presenting features of technogenic iron oxide reducing under conditions of solid-phase diffusion (limited diffusion) and partially liquid-phase diffusion (easier diffusion) of iron oxide ions. It is shown that under conditions of iron oxide ions solid-phase diffusion the reduction processes rate is significantly affected by the briquetting pressure, which increases the contact area of reacting substances. The briquetting pressure does not affect the reduction processes rate under conditions of partially liquid-phase diffusion of iron oxide ions. An ion-diffusion catalytic mechanism is proposed to describe the observed effects of technogenic iron oxide reducing.

The article deals with issues of integrated waste-free processing of electric arc furnaces dust. It is shown that it is possible to obtain a whole range of valuable commodity products on both metal and non-metal bases as a result of the electric arc furnaces dust complex processing. Integrated waste–free processing reduces the arc furnaces dust impact on the environment and produces a number of valuable commercial products.

Extraction of zinc from sulphide forms by pyrometallurgical methods is difficult due to the high energy of the “zinc-sulfur” bond. Theoretically justified and experimentally confirmed the possible methods of extracting zinc from such compounds by changing of raw material phase composition. The zinc oxide obtained by this way has high purity and does not require additional purification by hydrochemical methods.

There are millions of tons of solid waste residues accumulated in present-day alumina industry. Those solid waste residues contain red mud and belit mud. The creation of sludge depository, its keeping and taking environmental protection measures cost up to $8-12 million a year. However, red mud is a valuable raw material. The extraction of some useful elements from red mud makes it possible to obtain such valuable products as pig iron, iron-bearing concentrate, rare-earth elements, alumina concrete, constructional materials, etc.

There are two main kinds of slag in modern steelmaking industry: the electric arc furnace slag (the EAF slag) which is produced in the manufacture of crude steel by the electric arc furnace process and the ladle furnace basic slag (the LF slag) which is produced at the final stages of steelmaking, when the steel is desulfurized in the transport ladle, during what is generally known as the secondary metallurgy process.